AMD’s backtracking on Mantle — taking the API from a cross-platform development tool to ease the transition of code between PC and console on GCN hardware to a tool that allows for a more “console-like developer environment” — has killed one developer’s enthusiasm for the upcoming API.

Speaking on a panel at Nvidia’s “Way its meant to be played” event in Montreal this past weekend John Carmack said that should Microsoft and Sony embrace Mantle it would be “very powerful for AMD”, but should the API be a PC-only affair it would mitigate his interest in it.

“Mantle is unique. AMD has talked many times in the past about doing “close to the metal” architectures, and it only became interesting because of their dual console wins,” Carmack said on stage. “The landscape does matter because they have both major console wins with similar architectures that you can get on the PC.”

“If it was just a way to do, on the PC, lower-level [coding] I couldn’t have cared less.”

“If I was still doing all of the major tech coding,” he continued, “I probably would not be embracing Mantle right now. But there would be days where it would be extremely tempting.”

In early October Carmack tweeted that he believes Nvidia’s OpenGL extensions can provide a similar number of draw calls as Mantle. The ability to do nine times more draw calls is one of Mantle’s major selling points.

@relativegames 9x draw calls is credible over stock D3D, but Nvidia OpenGL extensions can give similar I mprocements.

Later on during the talk Carmack and the other panelists — Epic Games’ Tim Sweeney and DICE’s Johan Andersson — were asked if they thought other developers should follow AMD’s cue and create their own APIs. All agreed it was a bad idea.

“It’s the wrong direction for the industry to go,” said Sweeney. “If you’d ask me if I’d much rather have a low level API for accessing the GPU, the answer is yes. But five of them, for different hardware, vendors and operating systems? Absolutely not.”

“If Nvidia and Intel and Qualcomm did their own APIs, that would be a bad future,” added Andersson.

“My response to this would be Unequivocally no. It would be a horrible mistake if Nvidia got panicked by this and made some lower level API as you already have good low-level access through Nvidia’s GPU extensions,” said Carmack.

Of course the only one on stage with in-depth knowledge of Mantle was DICE’s Andersson, as Battlefield 4 is set to be a Mantle launch title. But while Andersson has substantial insight into Mantle, and could likely provide a few rebuttals to what the other panelists said on stage, his lips are sealed until AMD’s APU Developer Summit in San Jose.